The effect of nutrition during pregnancy on the in vitro production of embryos from resulting lambs

It is possible to produce offspring from FSH-treated lambs using in vitro maturation and fertilisation procedures but a major constraint is the high embryo wastage after transfer. It is postulated that this wastage is associated, at least in part, with the quality of the harvested oocytes. The aim of this study was thus to determine if nutrition during pregnancy influenced the quality of oocytes collected from resulting lambs. The study was a 2x2x2 factorial that examined the effect of a low (L; 0.7x maintenance) or high (H; 1.5x maintenance) diet provided during three periods (-82 to 70, 71-100 and 101-126 days relative to the date of conception). There were eight treatments namely LLL, LLH, LHL, LHH, HLL, HLH, HHL and HHH. Oocytes were harvested from 9-week-old lambs, matured and fertilised in vitro and the percentages of oocytes and embryos that developed into blastocysts were recorded. There were significant differences between treatments in oocyte and embryo yields and these resulted from complex interactions between diet and the stage of pregnancy. The efficiency of producing blastocysts from oocytes was highest when a H diet was provided between 71 and 110 and/or 101-126 days of pregnancy. These results demonstrate the need to manage nutrition during pregnancy in programs aimed at producing offspring from juvenile animals.